The Northern Irishman quit with the Hoops' bid to win a 10th straight title in disarray.
Neil Lennon has resigned as Celtic manager, with the reigning champions 18 points behind Rangers in the Scottish Premiership.
The 49-year-old, who returned to the club for a second stint in charge after Brendan Rodgers left to take over at Leicester in February 2019, had previously maintained he would not quit despite mounting pressure, with the Hoops' bid to win a 10th straight title in disarray.
Here, the PA news agency looks at the midfielder-turned-manager's Celtic career in pictures.
Neil Lennon completed a dream move to boyhood club Celtic from Leicester for £5.7million in December 2000 (PA)Lennon helped Celtic seal the treble with victory over Hibernian in the Scottish Cup final in May 2001 (Gareth Copley/PA)They retained the Scottish Premier League title the following year (Nick Potts/PA)Lennon helped Celtic reach the 2003 UEFA Cup final, where they suffered an extra-time loss to Porto (Maurice McDonald/PA)Lennon was involved in the odd bit of bother now and then (Mary McCartney/PA)A late red card in an Old Firm defeat to Rangers in 2005 (Steve Welsh/PA)Lennon and his autobiography – 'Man and Bhoy' – at Celtic Park in August 2006 (Andrew Milligan/PA)Celebrating another league title with son Gallagher in April 2007 (Chris Clark/PA)Lennon joined the Celtic coaching staff in 2008 (Michael Boyd/PA)Lennon was appointed Celtic caretaker manager in March 2010 following the departure of Tony Mowbray, and was unveiled as permanent manager in June of that year (Lynne Cameron/PA)An altercation with a fan at Tynecastle in 2011 (Lynne Cameron/PA)After a famous win over Barcelona in November 2012 (Lynne Cameron/PA)Just over a week after leading Celtic to another league trophy in May 2014, Lennon resigned. He was appointed Bolton boss five months later (Danny Lawson/PA)He returned for a second stint at the Hoops' helm in February 2019, appointed until the end of the season following Brendan Rodgers' departure for Leicester (Jane Barlow/PA)Three months later, the Northern Irishman was celebrating the treble and was handed the permanent reins once again (Jeff Holmes/PA)An Old Firm rivalry with Rangers counterpart Steven Gerrard (Ian Rutherford/PA)The Scottish Premiership season was suspended in March 2020 due to the coronavirus pandemic, with Celtic's 'nine in a row' feat declared two months later (Andrew Milligan/PA)Sunday's defeat at Ross County proved to be Lennon's final match in charge (Jeff Holmes/PA)
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